In WCDMA (Wideband CDMA) systems, the wireless receiver must demodulate and decode data effectively across a wide range of operating conditions. Some operating conditions that affect receiver performance include channel dispersion, receiver speed and channel geometry (the ratio of transmitter power to cumulative interference plus noise power). Ideally, a wireless receiver should obtain the best possible performance given the operating conditions. One approach to maximize performance is a fixed receiver configuration. Alternatively, the receiver can detect operating conditions and re-configure itself (adaptive configuration).
To obtain the best possible performance given the operating conditions, a fixed configuration receiver must be designed to handle worst-case operating conditions. For example, the wireless receiver must be equipped to handle extremely high speeds and a highly dispersive channel as well as no motion and a flat channel. Such a receiver would be extremely expensive in terms of power, computational complexity, and chip area, and is thus not practical. In contrast, a limited fixed receiver configuration focuses on a particular range of operating conditions to reduce receiver cost and complexity. While this approach generally works well for the expected range of operating conditions, overall receiver performance degrades when actual operating conditions differ from the expected operating conditions. The degradation can be significant and seriously impact the ability of the receiver to offer, for example, both peak data rates and robust performance at low SIR (Signal-to-Interference Ratio).
Other types of conventional receivers have a reconfigurable equalizer. In some cases, the equalizer is reconfigured as a function of receiver speed. For example, a nonparametric equalizer is employed at low speeds whereas a parametric equalizer is employed otherwise. In other cases, the equalizer is reconfigured as a function of channel dispersion. For example, the equalizer may employ a grid of equalizer fingers (symbol-level) or equalizer taps (chip-level) spaced at equidistant intervals. The grid spacing and extent (i.e. number of fingers/taps) is then varied as a function of channel dispersion. In each of these cases, only the equalizer is reconfigured as a function of either receiver speed or channel dispersion, limiting receiver adaptability.